Sabine M. Görisch a, Karsten Richter a, Markus O. Scheuermann a, Harald Herrmann b and Peter Lichter a, @
a Division of Molecular Genetics, Deutsches Krebsforschungszentrum,
Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany
b Division of Cell Biology, Deutsches Krebsforschungszentrum,
Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany
@ Corresponding author. Fax: +49-6221-424639
E-mail: m.macleod@dkfz.de
In order to investigate the accessibility of the nucleoplasm for macromolecules with different physical properties, we microinjected FITC-conjugated dextrans of different sizes as well as anionic FITC-dextrans and FITC-poly-L-lysine into mammalian cell nuclei. Small dextrans displayed a homogenous nuclear distribution. With increasing molecular mass (42 to 2500 kDa), FITC-dextrans were progressively excluded from chromatin regions, accumulating in and thereby outlining an apparently extended interchromatin space. Anionic FITC-dextrans (500 kDa) showed complete exclusion from labeled chromatin regions, while the positively charged FITC-poly-L-lysine was to some extent present within the chromatin regions. Moreover, the FITC-poly-L-lysine preferentially localized at the nuclear periphery. We also found a size-dependent exclusion of FITC-dextrans from nucleoli regions, while the FITC-poly-L-lysine accumulated in the nucleoli. Thus, the distinct and restricted nuclear accessibility for macromolecules is dependent on molecule size and electrical charge.
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